An exciton is an electron-hole bound pair in a semiconductor. In the low-density limit, it is a composite Bose quasi-particle, akin to the hydrogen atom. Just as in dilute atomic gases, reducing the ...temperature or increasing the exciton density increases the occupation numbers of the low-energy states leading to quantum degeneracy and eventually to Bose-Einstein condensation (BEC). Because the exciton mass is small-even smaller than the free electron mass-exciton BEC should occur at temperatures of about 1 K, many orders of magnitude higher than for atoms. However, it is in practice difficult to reach BEC conditions, as the temperature of excitons can considerably exceed that of the semiconductor lattice. The search for exciton BEC has concentrated on long-lived excitons: the exciton lifetime against electron-hole recombination therefore should exceed the characteristic timescale for the cooling of initially hot photo-generated excitons. Until now, all experiments on atom condensation were performed on atomic gases confined in the potential traps. Inspired by these experiments, and using specially designed semiconductor nanostructures, we have collected quasi-two-dimensional excitons in an in-plane potential trap. Our photoluminescence measurements show that the quasi-two-dimensional excitons indeed condense at the bottom of the traps, giving rise to a statistically degenerate Bose gas.
Exposure of control (non-hardened) Arabidopsis leaves to high light stress at 5 °C resulted in a decrease of both photosystem II (PSII) (45 %) and Photosystem I (PSI) (35 %) photochemical ...efficiencies compared to non-treated plants. In contrast, cold-acclimated (CA) leaves exhibited only 35 and 22 % decrease of PSII and PSI photochemistry, respectively, under the same conditions. This was accompanied by an accelerated rate of P700+ re-reduction, indicating an up-regulation of PSI-dependent cyclic electron transport (CET). Interestingly, the expression of the NDH-H gene and the relative abundance of the Ndh-H polypeptide, representing the NDH-complex, decreased as a result of exposure to low temperatures. This indicates that the NDH-dependent CET pathway cannot be involved and the overall stimulation of CET in CA plants is due to up-regulation of the ferredoxin–plastoquinone reductase, antimycin A-sensitive CET pathway. The lower abundance of NDH complex also implies lower activity of the chlororespiratory pathway in CA plants, although the expression level and overall abundance of the other well-characterized component involved in chlororespiration, the plastid terminal oxidase (PTOX), was up-regulated at low temperatures. This suggests increased PTOX-mediated alternative electron flow to oxygen in plants exposed to low temperatures. Indeed, the estimated proportion of O2-dependent linear electron transport not utilized in carbon assimilation and not directed to photorespiration was twofold higher in CA Arabidopsis. The possible involvement of alternative electron transport pathways in inducing greater resistance of both PSII and PSI to high light stress in CA plants is discussed.
Here we report a pilot-sized study to compare the taxonomic composition of sputum microbiome in 17 newly-diagnosed lung cancer (LC) patients and 17 controls. Another object was to compare the ...representation of individual bacterial genera and species in sputum with the frequency of chromosomal aberrations in the blood lymphocytes of LC patients and in controls. Both groups were male; average age 56.1 ± 11.5 in patients and 55.7 ± 4.1 in controls. Differences in the species composition of bacterial communities in LC patients and controls were significant (pseudo-F = 1.94; p = 0.005). Increased prevalence in LC patients was detected for the genera Haemophilus and Bergeyella; whereas a decrease was observed for the genera Atopobium, Stomatobaculum, Treponema and Porphyromonas. Donors with high frequencies of chromosomal aberrations had a significant reduction in the microbiome of representatives of the genus Atopobium in the microbiome and a simultaneous increase in representatives of the species Alloprevotella compared to donors with a low level of chromosomal aberrations in lymphocytes. Thus, a comparison of the bacterial composition in the sputum of donors with cytogenetic damages in theirs lymphocytes, warrants further investigations on the potential role of microorganisms in the process of mutagenesis in somatic cells of the host body.
Preliminary results of measurement of the cross section for the process
in the range of c.m. energies between 1.075 and 1.975 GeV are presented. An analysis was performed on the basis of an ...integrated luminosity of 62.9 pb
accumulated by employing the CMD-3 detector within the experimental runs of 2019. The suppression of the background from the processes
,
, and
and the background of cosmic-ray muons was accomplished with the aid of information about specific energy losses of charged particles in the layers of the liquid xenon calorimeter of the CMD-3 detector. The preliminary results of the present measurement of the
cross section are in reasonable agreement with the results of earlier measurements and have a commensurate statistical precision.
The Yakutsk Extensive Air Shower Array has been continuously operating for more than 50 years (since 1970) and up until recently it has been one of world’s largest ground-based instruments aimed at ...studying the properties of cosmic rays in the ultra-high energy domain. In this report we discuss results recently obtained at the array—on cosmic rays’ energy spectrum, mass composition and directional anisotropy—and how they fit into the world data. Special attention is paid to the measurements of muonic component of extensive air showers. Theoretical results of particle acceleration at shocks are also briefly reviewed. Future scientific and engineering plans on the array modernization are discussed.
Based on the example of an automated module of a vertical farm for growing plants, an author’s method for developing automated devices using modern microcontrollers and a high-level microPython ...programming language is proposed. Additive technology as a method of “rapid prototyping” made it possible to effectively solve the issue of creating the main components of the module. The works on designing, assembling, and adjusting the experimental setup were carried out using modern methods and approaches for the industrial development of devices. The automated system makes it possible to solve the problems of lack and selection of the correct dosage of nutrients necessary for plants, controls, and minimizes water consumption, the root system develops fully. These factors make it possible to grow an adult plant in a short time without human participation. The apparatus can be used for organizing research activities in the subject areas of the natural science cycle, for greening in corridors and classrooms, and growing fresh herbs.
Electrolyte additions are used to control the functionality of a nanostructured oxide. Dopant ions affect the size and shape of deposit crystallites and modify the host structure. Such ions can be ...incorporated into the deposit or form a separate oxide phase. The manganese dioxide family of polymorphs with ion-molecular sieve properties represents the additional possibilities of “template” effects of dopant ions on the phase composition, heterovalent substitution in the cationic sublattice, changes in morphology and alteration of nanocrystallite size during electrocrystallisation. The effects of electrolyte doping in electrodeposited, non-stoichiometric manganese dioxide (NH4+, Li+ and Co2+), chromium oxide-based films (Co2+, Li+) were investigated. The structural characteristics and morphology were studied for all the obtained nanocomposites and deposits were evaluated as highly crystalline cathode materials cathodes, having high cyclability, in Li batteries.
The improved functionality of the electrodeposited nanomaterials was correlated to structural changes. Hollandite and pyrolusite electrodeposition pathways were proposed, based on symmetry principles of phase transitions.
Display omitted
•Electrolyte doping for powdered MnO2 and CrxOy thin films have advantages vs conventional electrodeposition;•Hollandite and pyrolusite formation pathways can be derived from symmetry principles of phase transitions;•Semi-amorphous, isostructural series of ramsdellite-heterogenite like products at heavy Co + Li doping was established.•Cyclability of Co-doped CrxOy thin film coatings in Li batteries is demonstrated.
Display omitted
•MFI zeolites steamed at 550–750°C were studied in phenol oxidation with N2O.•Steamed zeolites may show 70% N2O conversion with selectivity to DHB exceeding 90%.•Steaming temperature ...affects strongly on coking and isomer distribution of DHB.•Steaming reduces zeolite acidity and changes isomer distribution in favor of catechol.
Gas-phase oxidation of phenol to dihydroxybenzenes (DHB) with nitrous oxide was performed over a set of ZSM-5 zeolites steamed at different temperatures in the range from 550 to 750°C. The best of the catalysts demonstrated 70% N2O conversion and a more than 90% selectivity for DHB. However, significant differences were observed in DHB isomer distribution and catalyst deactivation due to changes in the acidity of the zeolites. The steaming procedure reduces the concentration of Bronsted acid sites, thus allowing a decrease in coke loading. Simultaneously, a substantial decline in the molar ratio of hydroquinone to catechol in the reaction products was observed, mainly due to the increased selectivity to the ortho isomer – catechol. These results can be used to control the selectivity for different DHB isomers in the title reaction by varying steaming severity.
Posttranslational modifications in fibrinogen resulting from induced oxidation or oxidative stress in the organism can have deleterious influence on optimal functioning of fibrinogen, causing a ...disturbance in assembly and properties of fibrin. The protective mechanism supporting the ability of fibrinogen to function in ROS-generating environment remains completely unexplored. The effects of very low and moderately low HOCl/−OCl concentrations on fibrinogen oxidative modifications, the fibrin network structure as well as the kinetics of both fibrinogen-to-fibrin conversion and fibrin hydrolysis have been explored in the current study. As opposed to 25 Μm, HOCl/−OCl, 10 μM HOCl/−OCl did not affect the functional activity of fibrinogen. It is shown for the first time that a number of Met residues, AαMet476, AαMet517, AαMet584, BβMet367, γMet264, and γMet94, identified in 10 μM HOCl/–OCl fibrinogen by the HPLC-MS/MS method, operate as ROS scavengers, performing an important antioxidant function. In turn, this indicates that the fibrinogen structure is adapted to the detrimental action of ROS. The results obtained in our study provide evidence for a protective mechanism responsible for maintaining the structure and functioning of fibrinogen molecules in the bloodstream under conditions of mild and moderate oxidative stress.
•Fibrinogen treated with 10 μM HOCl/−OCl did not lose the functional activity.•Methionines in fibrinogen were the main target for 10 μM HOCl/−OCl.•Some of Met residues in the fibrinogen structure operate as endogenous antioxidants.•The fibrinogen structure is supposed to be adapted to the action of ROS.
PDF
